In a rack and pinion steering system, the pinion is coupled to a steering wheel and engaged with the rack such that turning of the steering wheel rotates the pinion thereby imparting movement to the rack. Moreover, the rack in a conventional rack and pinion steering system is cooperatively engaged with a pair of dirigible wheels so that movement of the rack imparts a change in direction for the dirigible wheels.
With a rack and pinion power steering system, a pressure source develops pressurized fluid and a rotary valve coupled to the pinion communicates the pressurized fluid to pressure chambers to assist the rack in its movement with the rotating pinion to change the direction of the dirigible wheels.
U.S. patent application Ser. No. 765,499 is a related rack and pinion power steering system wherein a rack carries a valve member for controlling fluid communication to a pair of chambers to provide a power assist to the movement of the rack.